This invention relates to a projection illumination system and apparatus therein, and more particularly to a system employable for tricolor projection, wherein, for a given light source energy level, a much higher percentage, and therefore higher intensity, of light emanates from the system than is possible with prior known projection systems. A preferred embodiment of the invention is described herein in the setting of tricolor video projection--an environment wherein the invention has been found to offer particular utility.
In the field of this invention, a consideration which looms as an ever present, significant hurdle and challenge relates to the obtaining of maximum intensity output for a given size or power level of source light. An important objective toward which prior art developments have aimed has been to produce a light projection system which can create on, for example, a projection screen at a "reasonable distance" from the projection structure, a brilliant, high-light-intensity image which can be viewed easily even in fairly bright ambiently illuminated space.
A key object of the present invention is to provide a projection system which takes a handsome advance toward achieving this objective by providing an organization of light source and optical elements, or components, which, for a given size of source light, can achieve significantly more output light than is attainable by the best known prior art competitive projection structures.
In a typical projection system, a source light is positioned at the focal point of a parabolic mirror located on one side of the light source and "aimed" on the system's projection axis. Such a "one-side-gathering" mirror gathers, at most, about 50% of the total light produced by the source, and, because of expected and unavoidable reflection losses, reflects only about 90% of this gathered light toward the usual optically "downstream" lens. The lens in such an arrangement ususally does not play any significant role in light-gathering directly from the source light.
By way of sharp contrast, and according to a preferred embodiment of the present invention, the same, at its core, is based upon a dual-side light-gathering arrangement which is very effective, and which includes, fundamentally, three coacting elements: (a) a selected, high-intensity source light: (b) a total internal reflection (TIR) lens structure: and (c) a reflector disposed in the system on the opposite side of the light source in relation to the TIR lens structure. The light source is spaced in close physical relation to the TIR lens structure in a fashion whereby one, fairly larger-percentage portion of output light from the source directly impinges a light-gathering surface expanse in the lens structure, with the reflector (preferably one having spherical curvature) gathering another, fairly large-percentage portion of light from the source, and redirecting this light also toward the same light-gathering surface expanse in the lens structure.
With the arrangement of the system proposed according to this invention operating, a major percentage (more than 50%) of the light which is radiated by the light source is directed toward the TIR lens structure for outputting from the system. Experience has shown that the organization proposed by this invention, for a given size or power level of source light, is capable of outputting up to about 50% more light than that which can be output utilizing the best known prior art type systems.
Yet another object of this invention is to provide a projection system of the type just generally outlined which is very simple in construction, relatively low in cost, and easily employed in a wide variety of light-projection structures and settings.
These and other objects and advantages which are attained by the present invention will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings.